1. Technical Field
This invention is related to the field of ignition diagnosis systems of automotive internal combustion engines. More particularly, it is related to the field of ignition diagnosis and control systems.
2. Discussion
The prior art includes a variety of conventional methods for detecting and using ionization current in a combustion chamber of an internal combustion engine. However, each of the various conventional systems suffers from a great variety of deficiencies. For example, prior art ionization current detection circuits are generally too slow and generate a current signal with low signal-to-noise ratio.
The spark ignition engine combustion process is governed by the in-cylinder air to fuel ratio, temperature and pressure, exhaust gas re-circulation rate, ignition time and duration, and other factors. Due to the high cost of an in-cylinder pressure sensor, engine spark timing is controlled in an open loop and is corrected using a knock detection result. As a result of open loop control, the engine combustion process is sensitive to operational conditions, engine-to-engine variation, engine aging, and other related factors.